Phosphine- and Amine-Borane Dehydrocoupling Using a Three-Coordinate Iron(II) β-Diketiminate Precatalyst

Abstract

Dehydrocoupling of phosphine- and amine-boranes is reported using an iron(II) β-diketiminate complex. Dehydrocoupling of amine-boranes is far more facile than the phosphine counterpart, the former proceeding at room temperature with 1 mol% iron precatalyst. This low loading is sufficient to allow in situ kinetic analysis and deuterium labeling studies to be carried out. An iron amido-borane complex has also been isolated, which is believed to be the catalyst resting state. Overall, this has allowed us to postulate a catalytic cycle which proceeds via release of diborazane, iron hydride, and iron amido-borane intermediates.